July, 1914.] THE APPLE MAGGOT. 45 



nearly normal as possible. Much difficulty was experienced in 

 accomplishing this. In fact, the larger the cage built, and the 

 more nea,rly the conditions appeared to approach normal, the 

 more apt the flies were to refuse to live out their existence to full 

 period and in rational manner. 



Nevertheless some egg-laying was done, and definite facts 

 were ascertained as to the possible minimum length of the period 

 after emergence of the female before egg-laying may begin. 

 These facts were both unexpected and interesting. 



It was proved that in some instances at least the length of this 

 period may be less than one week. In one case, in 1913, a fertile 

 egg was laid by a female only four days after emergence. In 

 1911 there was one definite case of a six-day period, and one of 

 an eight-day period. In the few other cases where definite 

 results were secured the period was longer; it is of course possible 

 that in these instances the females concerned were ready to 

 begin egg-laying earlier. Very few eggs were laid in total, or 

 at least very few were detected. 



It is not assumed from this that the normal length of this 

 period is one week or less; but it is certain that the period may 

 be this brief on occasion and that the two to three weeks hith- 

 erto assumed as the approximate minimum does not alwaj'S 

 prevail. 



Experiments in 1911. In 1911 four dwarf apple trees, stand- 

 ing about four feet high and located in the college orchard at 

 Durham, were enclosed in screen wire cages. Each cage was 

 3 feet 4 inches square on the ground and 4 feet high. In one 

 side was a small door. 



Beginning June 29, 1911, flies were released in these cages. 

 The flies placed in each cage were newly emerged from pupae 

 secured the previous year. All flies released in a cage on a 

 given date were of the same day's emergence, and no others were 

 released in this cage until all of the first lot had died or been 

 removed. In each cage at frequent intervals apples were placed 

 that were known to be free from infestation, the apples having been 

 bagged as they hung on the trees before any emergence of flies 

 had taken place. These apples were tied to the limbs of the 

 dwarf trees within the cages. Apples remained in the cages for 

 two to six days, and were then removed and placed on soil in 



